Stanford Research Systems SR830 Specifications Sheet

SR810 and SR830
DSP Lock-In Amplifiers

DSP LOCK-IN
AMPLIFIERS

SR810

Single Phase...$3650

SR830

Dual Phase...$3950

• 1 mHz to 102 kHz frequency range

(U.S. list)

(U.S. list)

he new SR810 and SR830 are
the latest additions to the

SRS family of DSP Lock-In

T

Amplifiers. The SR830 simultan­eously measures the magnitude and
phase of a signal, while the SR810
measures the magnitude of a signal at
a specific phase. Both instruments
use digital signal processing (DSP) to
replace the demodulators, output fil­ters and amplifiers found in conven­tional lock-ins. The SR810 and
SR830 provide uncompromised per­formance with an operating range of
1 mHz to 102 kHz and 100 dB of
drift-free dynamic reserve, outper­forming all analog lock-ins.

Extended Dynamic Reserve

• 100 dB dynamic reserve without
pre-filtering (< 5 ppm stability)

• Auto-gain, phase and reserve

• Time constants from 10 s to 30 ks
(6, 12, 18, 24 dB/oct rolloff)

• Harmonic detection (2F, 3F, ... nF)

• Synthesized reference source

• Four 16-bit ADCs and DACs

• GPIB and RS-232 interfaces

Conventional lock-in amplifiers use
an analog demodulator to mix an
input signal with a reference signal.
Dynamic reserve is limited to about
60 dB, and these instruments suffer
from poor stability, output drift and
excessive gain and phase error.
Demodulation in the SR810 and
SR830 is accomplished by sampling
the input signal with a high precision
A/D converter, and multiplying the
digitized input by a synthesized
reference signal. This digital demod­ulation technique results in more than
100 dB of true dynamic reserve (no
pre-filtering) and is free of the errors
associated with analog instruments.
Using DSP, a small signal embedded
in noise that’s a million times larger
can easily be measured.

Digital Filtering

Frequency Synthesizer

The digital signal processor also han­dles the task of output filtering, allow­ing time constants from 10 µsec to
30,000 sec, with a choice of 6, 12, 18
and even 24 dB/oct rolloff. For low
frequency measurements (below
200 Hz), synchronous filters can be
engaged to notch out multiples of the
reference frequency. Since the har­monics of the reference have been
eliminated (notably 2F), effective out­put filtering can be achieved with
much shorter time constants.

Digital Phase Shifting

Analog phase shifting circuits have
also been replaced with a DSP calcula­tion. Phase is measured with 0.01°
resolution and the X and Y outputs are
orthogonal to 0.001°. This represents
a significant improvement over analog
instruments.

The built-in direct digital synthesis
(DDS) source generates a very low
distortion (-80 dBc) reference signal.
Single frequency sinewaves can be
generated from 1 mHz to 102 kHz
with 4 1/2 digits of resolution. Both
frequency and amplitude can be set
from the front panel or from a comput­er. When using an external reference,
the synthesized source is phase locked
to the reference signal.

Easy Operation

Unlike some lock-in amplifiers, the
SR810 and SR830 are simple to use.
All instrument functions are set from
the front panel keypad, and a spin
knob is provided to quickly adjust
parameters. Up to nine different
instrument configurations can be
stored in non-volatile RAM for fast
and easy instrument setup. Standard
RS-232 and GPIB (IEEE-488) inter-

faces provide communication with
computers. All functions can be
controlled and read through the inter­faces.

Useful Features

Auto-functions allow parameters that
are frequently adjusted to automatical­ly be set by the instrument. Gain,
phase, offset and dynamic reserve are
each quickly optimized with a single
key press. The offset and expand fea­tures are useful when examining small
fluctuations in a measurement. The
input signal is quickly nulled with the
auto-offset function, and resolution is
increased by expanding around the
relative value by up to 100 times.
Harmonic detection is no longer
limited to only the 2F component.

Any harmonic (2F, 3F, ... nF) up to
102 kHz can now be measured without
changing the reference frequency.

Analog Inputs and Outputs

The SR810 and SR830 have a voltage
input sensitivity range that extends
from 2 nV to 1 V. A current input is
also provided with a choice of 106or
108volts/amp gain ratio. Both instru­ments have a user-defined output for
measuring X, R, X-noise, Aux1,
Aux 2 or the ratio of the input signal to
an external voltage. The SR830 has a
second user-defined output that mea­sures Y, Θ, Y-noise, Aux 3, Aux 4 or
ratio. The SR810 and SR830 both
have X and Y analog outputs (rear

panel) that are updated at 256 kHz.
Four auxiliary inputs (16-bit ADCs)
are provided for general purpose use,
like normalizing the input to source
intensity fluctuations. Four program­mable outputs (16-bit DACs) provide
voltages from -10.5 V to +10.5 V and
are settable via the front panel or
computer interfaces.

Internal Memory

The SR810 has an 8,000 point
memory buffer for recording the time
history of a measurement at rates up to
512 samples/sec. The SR830 has two
16,000 point buffers to simultaneously

record two measurements, like R
and Θ. Data is transferred from the
buffers using the computer interfaces.
A trigger input is also provided to
externally synchronize data recording.

Absolute Value

The SR810 and SR830 DSP Lock-In
Amplifiers from Stanford Research
Systems offer outstanding perfor­mance, features, and value. Specif­ication by specification, feature by
feature, no other lock-ins can compare.

Specifications

SIGNAL CHANNEL

Voltage inputs Single-ended or differential
Sensitivity 2 nV to 1 V
Current input 10
Impedance Voltage: 10 MΩ + 25 pf, AC or DC

Gain accuracy ± 1%
Noise 6 nV/√Hz at 1 kHz (typical)

Line filters 60 [50] Hz and 120 [100] Hz notch

CMRR 90 dB at 100 Hz
Dynamic reserve > 100 dB without prefilters (< 5 ppm/°C)

6

or 108Volts/Amp

coupled
Current: 1 kΩ to virtual ground

0.13 pA/√Hz at 1 kHz (10

0.013 pA/√Hz at 100 Hz (10

(Q=4 )

6

V/A)

8

REFERENCE CHANNEL

Frequency range 0.001 Hz to 102 kHz
Reference input TTL or sine (400 mVp-p minimum)
Input impedance 1 MΩ, 25 pf
Phase resolution 0.01° front panel, 0.008° through

computer interfaces.
Absolute phase error < 1°
Relative phase error < 0.001°
Orthogonality 90° ± 0.001°
Phase noise Internal oscillator reference:

Synthesized, < 0.0001°rms at 1 kHz.

External reference applied: 0.005° rms

at 1 kHz, 100 ms, 12 dB/oct.
Phase drift < 0.01°/°C below 10 kHz,

< 0.1°/°C below 100 kHz.
Harmonic detection 2F, 3F, ... nF to 102 kHz (n<19,999).
Acquisition time 2 cycles + 5 ms or 40 ms (whichever is

larger)

DEMODULATOR

V/A)

DISPLAYS

Channel 1 4 1/2 digit LED display with 40 segment

LED bar graph. X, R, X-noise, Aux 1 or Aux

2. The display can also be any of these
quantities divided by Aux 1 or Aux 2.

Channel 2 (SR830) 4 1/2 digit LED display with 40 segment

LED bar graph. Y, Θ, Y-noise, Aux 3 or
Aux 4. The display can also be any of these
quantities divided by Aux 3 or Aux 4.

Offset X, Y, R can be offset up to ±105% of full

scale.
Expand X, Y, R can be expanded by 10 or 100.
Reference 4 1/2 digit LED display.

INPUTS AND OUTPUTS

CH1 output ± 10V output of X, R, X noise, Aux 1 or

Aux 2. Updated at 512 Hz.
CH2 output (SR830) ± 10V output of Y, Θ, Y noise, Aux 3 or

Aux 4. Updated at 512 Hz.
X, Y outputs In phase and quadrature components (± 10V).

Updated at 256 kHz. (Rear panel)
Aux. A/D inputs 4 BNC inputs, 16 bit, ± 10 V,

1 mV resolution, sampled at 512 Hz.
Aux. D/A outputs 4 BNC outputs, 16 bit, ± 10 V,

1 mV resolution.
Sine Out Internal oscillator analog output.
TTL Out Internal oscillator TTL output.
Data Buffer The SR810 has an 8,000 point memory

buffer. The SR830 has two 16,000 point

buffers. Data is recorded at rates up to

512 Hz and is read using the computer

interfaces.
Trigger In TTL signal synchronizes stored data

recording.
Remote pre-amp Provides power to the optional SR550 and

SR552 preamplifiers.

Stability Digital outputs and display: no drift.

Analog outputs: < 5 ppm/°C for all
dynamic reserve settings.

Harmonic rejection -90 dB
Time constants 10 µs to 30 ks (6, 12, 18, 24 dB/oct

rolloff). Synchronous filters available
below 200 Hz.

INTERNAL OSCILLATOR

Range 1 mHz to 102 kHz
Frequency accuracy 25 ppm + 30 µHz
Frequency resolution 4 1/2 digits or 0.1 mHz, whichever is

greater.

Distortion - 80 dBc (f<10kHz), -70 dBc

(f>10kHz) @ 1 Vrms amplitude.

Amplitude 0.004 to 5 Vrms into 10 kΩ (2 mV

resolution). 50 Ω output impedance. 50 mA
maximum current into 50 Ω.

Amplitude accuracy 1%
Amplitude stability 50 ppm/°C
Outputs Sine, TTL. (When using an external

reference, both outputs are phase locked to
the external reference)

GENERAL

Interfaces IEEE-488 and RS-232 interfaces standard.

All instrument functions can be controlled

and read through IEEE-488 or RS-232

interfaces.
Power 40 Watts, 100/120/220/240 VAC, 50/60 Hz.
Dimensions 17"W x 5.25"H x 19.5"L
Weight 23 lbs.
Warranty One year parts and labor on materials and

workmanship.

SR810 & SR830 Rear Panel

More About Dynamic Reserve

Dynamic reserve is defined as the ratio of the largest interfering signal or noise to full scale signal that can accurately
(<5%) be measured by a lock-in amplifier. For example, if full scale is 1 µV, then a dynamic reserve of 60 dB means
that noise as large as 1 mV (60 dB greater than full scale) won’t affect the measurement more than a few percent.
Analog lock-ins are limited to about 60 dB dynamic reserve and experience poor stability (> 500 ppm/°C) when
measuring a small signal in an extremely noisy environment. To achieve more than 60 dB dynamic reserve, they resort
to pre-filtering the input signal which degrades accuracy. Using DSP to replace the demodulator, amplifiers and output
filters found in analog lock-ins, the SR810 and SR830 are able to provide greater than 100 dB dynamic reserve
(< 5 ppm/°C) without pre-filtering, and measurements are free of the artifacts and limitations found in conventional
lock-ins.

The SR830 and an analog lock-in are both presented

Analog Lock-In
Amplifier

DSP Lock-In
Amplifier

with a 10 mV interference signal at 600 Hz, while
locked at 350 Hz. Under identical test conditions
(10 µV sensitivity, 60 dB dynamic reserve, 300 msec
output time constant with 12 dB/oct rolloff), the analog
instrument (top graph) exhibits an average error of
13% and varies up to 22% of full scale. In contrast,
the SR830 DSP Lock-In Amplifier (bottom graph) has
an average error of about 0.3% and the variation is
negligible.

Many lock-in manufacturers call their instruments “digital lock-in amplifiers” because of their front panel digital
controls, computer interfaces and microprocessor designs. But the heart of these instruments, the demodulator, is still
analog in nature. Using DSP to replace analog circuits with mathematical calculations, the DSP lock-ins from SRS
provide performance never before possible, and are true “digital lock-in amplifiers”. They have at least 40 dB more
dynamic reserve than their analog counterparts, and are the most effective lock-in amplifiers available for extracting a
small signal from a noisy background.

Ordering Information

SR810 Accessories

Single Phase Lock-In Amplifier $3650 SR540 Chopper $995 4 Hz to 4 kHz, 4 digit display,

SR830

Dual Phase Lock-In Amplifier $3950 input impedance.

(all prices U.S. list)

SR550 Preamplifier $495 3.6 nV/√Hz input noise, 100 M
SR552 Preamplifier $495 1.4 nV/√Hz input noise, 100 k

input control voltage.

Ω

Ω

input impedance.

1290 D Reamwood Avenue • Sunnyvale, CA 94089
Telephone [phone] • FAX: [phone]
E-mail: [e-mail] • www.thinkSRS.com

Printed in USA ©1993 Stanford Research Systems, Inc. All specifications and prices subject to change (7/93)